The Belize Aggressor IV is a great boat. I was on it a yr ago and had a great time. You do not have to go deep to have a great time and see plenty. I found it had the best customer service of any boat I have been on. You are in for a very nice trip! You can see photos of that trip at this link.
Belize Lighthouse and Turneffe Atolls - shiningseastudio
I suggest you partner up with another couple or other divers that have more experience and stick together. Several parties did that on my trip there. They stayed near the top of the reef, not too far from the boat and I think they saw as much and likely more than most of the other groups.
Navigation would be the main concern I would have for you. Each of you should have a good compass and practice with it. Its easy to have the reef on your left one way and right on the return (or the reverse) but sometimes you may want to go into the sand flats and see the rays, etc that are there and the reef may become out of sight. Good to know which way to get back to it. Its not hard but you need to be prepared for it by checking the compass anytime you are leaving the reef so you know which way to return and check it once in a while away from the reef.
Also, when you enter the water, take a good look at the reef so you know what to look for on your return. Look from the view you will return from, not just from the boat view. The boat may not be at that location when you return so you need to know what the site looks like. I will explain below.
The boat swings off of a single mooring during the dive due to wind and current. So the boat is sometimes at the place where you entered and sometimes it is not in sight for a while at that location. But in a few minutes it returns.
For example, I had returned to the original entry point and the boat was above me. I started taking a few photos and staying in that area as I was approaching the time limit for the dive. Two other divers arrived and asked me ‘where is the boat’? I looked up and it was nowhere in sight. So I motioned for them to wait HERE. In 2-3 minutes, the boat returned on its swing and we went up to be in position for it to pick us up. This is all explained in the dive briefing.
The boat swing can be much faster than you can move in the water so there is no point in trying to catch it. You see the swing and move into its path. There is a nice bar at 15 ft connected to the boat at both ends. You wait at 15 ft or so as the boat approaches and you grab on. You can do your safety stop from the bar.
If you miss it on the swing by, just wait and it will return again in another few minutes. Most of the time the reef top was less than 40 ft so air consumption/N2 loading is not too great while waiting for the boat to return.
There were times when the swing was quite fast. Hanging on to the bar was work and it felt like an amusement park ride. It was actually fun as you were not working, just hanging on. But less fun if you think you could catch it after it had passed. You have to wait for the return and keep calm and patient.
While hanging on the 15 ft bar, the crew drops down to you and removes your fins, takes any camera gear and you just hold onto the bar. When you are finished at the bar with the safety stop, you can hand over hand to the ladder and easily go up. You never need to touch your fins as they put them on before your dive and remove them afterwards. This may seem like overkill but I really liked it once I experienced it.
Once my group went to the mooring pin base (a large concrete block) as we were told it had nice blennys to photogragh. We tried to get to the boat by just following the mooring line back. Seems simple enough. But as you get further from the mooring base, the boat is swinging faster than you can adjust to it. It became an interesting sprint to be in position to catch the bar. But I could have just gone to where the boat was and wait for the return.
